It is extremely desirable and convenient to have secure methods for the reliable trace detection of substances in liquids, especially body fluids, where the presence of a concentration as low as 10−11 M of a substance may be potentially pathogenic.
Classical methods of detection in liquids are based on reaction mechanisms where either the appearance of a product or the disappearance of a reagent can be measured. Greater importance is given to chemiluminescent compounds, capable of producing light when in favorable conditions.
The chemiluminescence is a method based on certain substances characteristic of emitting light when in presence of the compound to be analyzed. It has applications in forensics, diagnosis and quality control fields, being capable of detecting traces of compounds. One example of a commonly used chemiluminescent substance in criminal investigations is luminol, capable of detecting blood stains hidden in suspicious locations, such as crime scenes. The mechanism of action of luminol is based on the reaction below, where the addition of hydrogen peroxide is capable of oxidizing the luminol in a basic medium, generating light. However, the reaction below needs a catalyst, which will be the iron (Fe) present on erythrocyte's hemoglobin of the blood. Hence, when a basic luminol solution is put in contact with a hydrogen peroxide solution with Fe, an intense glow will be produced, confirming the presence of the compound.

There are many applications for chemiluminescent substances besides forensics. Recently, there has been a demand and production increase, especially for entertainment and in accidents preventions industries. A number of accessories, such as bracelets, necklaces, earrings, plastic teeth frame, cups etc, are frequently used in events, residences, night clubs, theaters, stadiums, music festivals, rodeos and many others, drawing the attention of the public with the intense chemiluminescence reaction glow. Safety flares are used by scuba-divers in deep waters and poor visibility, especially in the maintenance of underwater industrial petrol plants maintenance, or by the police and fire department in case of night accidents with intense fog or in unfavorable weather conditions on roads and large avenues or by the coast guard, helping night sailing on rivers, bays and near the coast. These are some examples of the many applications of the chemiluminescent substances industrially produced by the process described on the present invention, specially the luminol.
Luminol and its derivatives synthesis process include, among other steps, the reaction of a dicarboxylic acid with a hydrazine. This stage is usually difficult to accomplish, since drastic conditions are needed and the yield is not significantly high. Some documents propose solutions to this stage.
British patent GB 1,100,911 is the first to describe the synthesis of phtalazine derivatives. Among the proposed processes, it uses a mixture of a dicarboxylic acid and a hydrazine, the mixture being heated under reflux for 4 hours. The solution is cooled and water and HCl are added until pH 7. The solid formed is recrystallized in hot water.
American patent U.S. Pat. No. 4,226,992 performs the formation of the phtalazide from a dicarboxylic acid and a hydrazine in methanol under reflux for 3 hours. After cooling, the mixture is evaporated until dryness in a rotoevaporator, and the crystalline residue dried overnight at 80° C. under vacuum.
American patent U.S. Pat. No. 4,226,993 describes the reaction of a phtalimide with a hydrazine, in ethanol for 2 hours under reflux, followed by cooling and rest overnight. After evaporation in rotoevaporator under reduced pressure, the solid was dried at 110° C. for 8 hours under a pressure of 0.1 mmHg. The solid residue was stirred for 90 minutes in HCl 10%, filtered and neutralized with KOH, and the precipitated was filtered, dried and recrystallized in aqueous dimethyl formamide
One document describing a technique similar to the present invention's is American patent U.S. Pat. No. 6,489,326. It describes an extremely dangerous and complex production process of a hydrazide from the 3-nitro-phtalic anhydride and hydrazine. In spite of presenting excellent yields, between 85 and 90%, the reaction involves a Ni-Raney catalyst, gas generation, such as N2 and H2, and is extremely exothermic, reaching temperatures of 285-90° C.
Unlike all the processes described above, the present invention uses a halide donator, more specifically chloride, even more specifically niobium pentachloride in dioxane, that promotes a smooth reaction, easy controlled and capable of generating 90-95% yield.
Niobium pentachloride is a known Lewis acid, used as a catalyst for cyclotrimetrization reactions, for example, reactions described in document WO 91/09066. Regarding the synthesis of organic compounds, an important document, though not relevant, is document U.S. Pat. No. 4,349,471, which describes the synthesis of sulfonic acid halides and aromatic carboxylic acids halides. The referred reaction involves the use of a Lewis acid, for example niobium pentachloride.
However, the reaction of the present invention is completely different from the reactions described on the above mentioned documents, and therefore the use of a Lewis acid halide donator, more specifically chloride, for example niobium pentachloride, aiming hydrazides synthesis from dicarboxylic acids and hydrazines have never been described before, being the present invention therefore new.